実験的脳死における延髄網様体の電気活動と腎交感神経および横隔膜神経の遠心性発射

ELECTRICAL ACTIVITIES OF THE BULBAR RETICULAR FORMATION, RENAL SYMPATHETIC NERVE AND PHRENIC NERVE DURING EXPERIMENTALLY INDUCED BRAIN DEATH IN THE CAT

緒言

　脳死で最も問題となるのは，消滅しつつある脳機能の回復の可能性の判定である。臨床的には，脳死には種々の段階があり，それは，種々の脳機能が，脳の比較的全般的な障害に対してもそれぞれ異なつた耐性を有するため，ある機能は消滅したままの状態で病変が固定するためである。

　脳死の判定基準として，日本脳波学会では次の項目をあげている^21）。

The effects of acute ischemic anoxia on the activities of CNS, renal sympathetic and phrenic nerve discharges in the gallamine-immobilized cats were studied.

The CNS activities monitored were EEG's and multiple unit activities (MUA) of the cerebral cortex, centre median nucleus of the thalamus, midbrain and bulbar reticular formation. These activities were observed both during ischemia and recovery periodfollowing clamping and unclamping the bilateral common carotid arteries of the cat, whose brain circularion was so modified that it was nourished by these arteries only. A careful evaluation was done on the relationship between bulbar MUA and the neurograms of renal and phrenic nerves. During ischemia the renal nerve maintained its activity as long as the bulbar MUA maintained more than 30% of the control. Below this level it decreased in parallel with the decrease of bulbar MUA. The phrenic nerve discharge was found to be less re-sistant to ischemia than that of the renal nerve. Following unclamping, the recovery of the phrenic nerve activity took place always later than that of the renal nerve. This delay was noted to be moreobvious in the respiratory rate than in the amplitude of nerve discharge during each inspiration.

The bulbar MUA showed a post-anoxic activation at the end of the recovery period. This was ac-companied by enhancement of the renal and phrenic nerve discharges, which suggested the existence of the chemical (CO₂)-sensitive neurons in this area. Post-anoxic convulsions occurred in some instances when the bulbar MUA showed post-anoxic activa-tion

It was confirmed that both spontaneous respiration and maintenance of normal blood pressure are re-liable signs of the viability of the brain stem core.